Brake and clutch assemblies, which utilize large diameter multiple stationary and rotating discs for the braking and clutching functions, generate considerable shock forces during operation of the brake or clutch. Various mechanisms have been used in an attempt to cushion and smooth the shock from freewheeling to a braking action. These prior art mechanism include a variety of shapes and sizes of spring elements.
One type of cushioning element used in a clutch or brake unit is shown in U.S. Pat. No. 3,353,641, issued to H. E. Chana on Nov. 21, 1967. In this patent, an annular elastomeric cushioning member is disposed in a groove formed in the face of a piston. As the friction plates are engaged in response to movement of the piston, the cushioning member initially deflects to provide a gradually increasing spring rate and gradual loading of the friction plates. Further movement of the piston increases the applying force of the cushioning member on the friction plates until the plates are in total intimate frictional contact. Deflection of the cushioning member is stated as being limited by the depth of the groove in the piston face, as the face of the piston becomes flush with the brake pack.
Another type of cushioning element is shown in U.S. Pat. No. 3,285,379, issued to C. A. Helquist on Nov. 15, 1966. The cushioning element disclosed in this patent is a circular wave spring and is shown being used in the environment of a fluid pressure clutch assembly. As in the previously noted patent, the wave spring is located within a groove in the face of the clutch actuating piston. Operation is also similar to the above noted patent, in that movement of the piston brings the wave spring into contact with a disc of the clutch assembly. Further movement of the piston causes the spring to yield and cushion the frictional engaging force between the friction discs of the clutch assembly. The piston face will engage the clutch disc before the wave spring bottoms out.
Although the above noted cushioning elements will provide a cushioning action for the engaging members of the brake and clutch assemblies, they would seem to provide less than the optimum spring rate characteristics, since only a portion of the brake load is cushioned. The force applying piston disclosed in each patent would be difficult and expensive to manufacture in view of the groove required in the face of the piston.
The present invention is directed to overcoming one or more of the problems as set forth above.